1. Field of the Invention
This invention relates to a semiconductor memory device having a three-dimensional memory cell array structure in which electrode layers are stacked to form memory cells densely arranged in the electrode stacking direction.
2. Background Art
Conventional stacked memory technology is based on the structure of layers stacked by repeating for each layer the process of forming normal, planar memory cells on a silicon substrate. This structure is unsuitable for large capacity because it requires many manufacturing steps per layer. In this context, a technique for increasing the capacity with high manufacturing efficiency is proposed (e.g., JP-A-2007-266143(Kokai)). In this technique, gate electrode layers and interlayer dielectric layers are alternately stacked into a stacked structure. Holes penetrating therethrough from the uppermost layer to the lowermost layer are formed at once, and silicon is buried therein in a pillar shape. In the resulting structure, the silicon pillar is covered with the gate electrode layers at certain intervals. A memory cell transistor is formed by providing a charge storage layer for data retention at the intersection between the gate electrode layer and the silicon pillar.
In such a collectively patterned stacked memory, to separate the memory cell array into a plurality of blocks, the stacked body including the word line electrode layers is divided by slits with an interlayer dielectric film buried therein. Furthermore, for electrical contact to each word line electrode layer, the end portion of the word line electrode layers is patterned into a staircase shape. In this staircase patterning, that is, in etching away the unwanted portion of the word line electrode layers, the word line electrode layer may partly remain beside the slit sidewall under the current process technology. Depending on the slit pattern layout, there is concern about the problem of short circuit between the word line electrode layers of adjacent blocks or regions across the slit through the residual electrode layers beside the slit.